Apparatus for making an asbestos product



Feb. 4, 1941. G. B. BROWN APPARATUS FOR MAKING AN ASBSTOS PRODUCTPatented Feb. 4, 1941 UNITED STATES PATENT OFFICE George B. Brown,Manville, N. J., assignor 'to Johns-Mauville Corporation, New York, N.Y., a.

corporation of New York Application January 25, 1938, Serial No. 186,793

2 Claims.

This invention relates to an apparatus for making an asbestos and cementproduct.

More particularly, the invention relates to sheets consisting largely ofasbestos and Portland cement, as, for example, in the form of shinglesor siding units. The invention will be illustrated, therefore, bydetailed description in connection with such sheets.

It is an object of the invention to provide an asbestos and cement sheetthat, for a given modulus of rupture, may be made thinner and,therefore, less expensive of materials than such a sheet made byconventional methods. Another object is to decrease the permeability ofasbestos and cement sheets to water. An additional object is theprovision of an improved apparatus for the manufacture of asbestos andcement products. Other objects and advantages will appear from thedetailed description that follows.

A preferred embodiment of the invention will be described in connectionwith the attached drawing, to which reference is made.

Fig. 1 shows diagrammatically a side elevation of an apparatus 'that maybe utilized with my method, in making the product of the invention.

Fig. 2 shows diagrammatically a plan view of the apparatus of Fig. 1, inthe direction of the arrows of line 2-2 of Fig. 1.

Fig. 3 shows a face View of the air-separating member to be describedlater.

Fig. 4 shows a perspective view of the finished asbestos and cementproduct.

The asbestos libres and Portland cement are used in the proportions andthe asbestos fibres are of quality and bre length that are conventionalin the manufacture of asbestos and cement sheets for any given purpose.Thus, in the manufacture of shingles or siding units, there 40 may beused relatively short chrysotile libres, as

for example, Canadian fibres showing practically nothing on li-mesh, 'lto 9 parts on lll-mesh, and 9 to 7 parts through the 10-mesh screen,when a 16-ounce sample is subjected to test by the Quebec standard, wetscreening method.

The proportions of asbestos and cement may be varied Within aconsiderable range, say 35 to 150% of asbestos on the weight of thePortland cement. In the detailed examples given below the cement andasbestos were used in approximately equal proportions by weight.

In addition to the asbestos and cement, there may be used pigments asdesired and various conventional admixtures Curing is eiected in usualmanner.

In general, raw materials in selected proportions are dispersed in airand are driven towards and deposited upon a felting member. There isthus formed on the felting member a layer of such thickness as to give,after the subsequent 5 steps in the process. a finished sheet of desiredcaliper. The layer is then approximately levelled. Water is applied.Preferably, an air-separator is used to eliminate from the layer excessof air,v that is, air which, if not removed, would later I0 causeblistering or weakness due to its escape under conditions unfavorable tothe strength of the product. Finally, the wet layer is shaped andstrongly compressed and the cement therein is hardened. l5

This general method may be performed, for example, by delivering theselected raw materials from a storage or hopper Il upon the movingconveyer l2, which discharges the material through opening I3 to themeans for forming an intimate dispersion of the raw materials in air.

Convenient dispersing means include beaters, `such as the spike rollersIt arranged in pairs and rotated at points between any given pair ofrollers, that is, at points on any roller nearest the other roller ofthe pair, in the direction of the felting member. In this manner. thedispersed material is driven in the direction of the felting member l5.The beaters or spike rollers may be driven at various speeds, dependingin part upon the size of the beaters and the degree of packing desiredon the felting member. Thus, with spike rollers of overall diameter of 7to 1l. inches, the rotation may be at the rate of about 200 to 1,000 R.P. M.

In the dispersion described, there is formed a suspension of the solidmaterials in a large volurne of air. Other inert gaseous media may beused, as a substitute for air, in forming the aeriform suspension.

I have used to advantage three sets of the coacting beaters, arrangedone set above another, so that all may coact to drive the dispersedmaterial towards the felting member. Deflectors i6 assist in directingthe dispersed material between the rollers of each pair.

The driving force of the beaters or spike rollers affect the quality ofthe felting on the member l5; for a certain weight of material persquare foot of the layer formed on the felting member, the thickness isabout 2 inches at a speed. of rotation of 200 R. P. M. for 9-inch spikerollers, and only approximately 1.5 inches when the speed of rotation isincreased to 1,000, other conditions being comparable.

The dispersing means are enclosed in an airlled container or cabinet l1.Ihe opening i3 at the top thereof for the introduction of the rawmaterials is preferably made relatively narrow, say about 2 inchesacross. This narrow opening limits the rate of entrance of air into thechamber.

In case excessive dusting is produced by the dispersing means described,the downward velocity of the air stream carrying the dispersed solidmaterials may be decreased by reversing the direction of rotation of onepair of the rollers, i. e. the middle pair, without affecting adverselyto any great extent the degree of dispersion and intimacy of the mixtureof the said materials in the air stream.

The chamber or housing Il opens at the bottom above the felting memberl5, which is suitably a moving conveyor of impermeable fabric, such as arubber or rubberized canvas of the type that is usual as the conveyer ondry process asbestos and cement shingle machines. In

its upper reach, this belt moves to the right in.

the arrangement shown in Fig. 1. The belt passes under the picker rollerI9 of the conventional type, which levels off the top of the depositedmaterial and throws any excess back into the screw or scroll conveyor I8which carries the excess to/ the side. Because of the relatively greatthickness of the air-felted material at the levelling stage, as comparedto the finished thickness of the product to be described, inaccuraclesof levelling are minimized in the finished, compressed sheet.

I n order to obtain best results, excess of air is then separated fromthe layer of material, as by pressing thereagainst a member ofair-permeable face, such as the rollers 20. The face of the roller isconstructed of perforated metal or the likel so that air may escape atclosely spaced positions, while, at the same time, the solid materialsof the layer do not adhere objectionably to the surface of the roller.The weightof the roller gives sufficient pressure. Movement downward ofthe air-separator is limited by stops (not shown) which preventexcessive compression at this stage. Suitable openings are of 11g to V9inch diameter.

The layer of asbestos and cement mixture is then passed under a roller2| of continuous or solid surface, for moderate compression and furthershaping.

Water is applied to the material, as at position 22, subsequent to thepassage of the layer under the roller 2l and/or at position 23.Ordinarily, I apply the water at both positions 22 and 23, the waterapplied at 23 being placed directly upon the conveyer belt before anysolid material is deposited thereupon and the water at position 22contacting directly with the top of the layer, so that water may enterthe layer from both face and back. About equal amounts of water may beapplied at each position.

The water may, however, be applied to the raw materials entering throughinlet I3. In this case, the amount of water used is restricted inquantity approximately equal to that required to hydrate the Portlandcement during the final setting or curing thereof, so as to avoidstickiness of the dispersed material. Thus, there may be usedapproximately 10 to 16% of water based on the Weight of the cement.

In all cases, the amount of water used is not less than that required tohydrate the Portland cement and is insuflicient to cause the wetmaterials to flow on the conveyer under the influence of gravity alone.Ordinarily, the amount of water used is enough to form a uniformly wet,stimy plastic mixture that ows only when subjected to great pressure.

The layer of material is then passed under a cutting roller Ed,advantageously after having been first passed under a second smoothingand compressing roller 25.' The cutter severs the continuous layer ofshaped material into segmentsl that may later be trimmed or cut to theexact length and breadth desired for the finished asbestos and cementsheets.

After the cutting, the segments may be passed under another smoothingroller 20.

Finally, they are removed from the conveyer and supported uponpractically rigid metal plates 2l, each as large or somewhat larger inarea than the segments.

A number of the supporting plates 21 and segments of material thereonare stacked one above another, with the metal plates 21 alternating withthe asbestos and cement sheets. then subjected to strong compression,under a hydraulic press at a pressure of approximately eight to tenthousand pounds per square inch.

If it is desired to make a sheet with a textured face, a texture plateof suitable pattern is inserted on top of each segment, before the stackis formed for the hydraulic compression.

Parts of the apparatus involved and steps in the process performed afterthe layer passes under the roller 2| are usual and may be varied inaccordance with conventional practice, except that the waterconventionally supplied at 22 is omitted in case all the water desiredhas been added previously, as in one modication of my process.

During the strong compression in the hydraulic press, escape of water ispermitted, as at the edges of the wet sheets being compressed, and thefinal shaping and consolidating of the layer is effected.

After the pressure is released, the compressed sheets are allowed tostand for about a day, during which time the cement takes its initialset. The sheets are then set, as, for instance, by long standing atatmospheric temperatures, or by steam curing for a few hours in casesand or silica has been admixed, as in the alternative compositiondescribed above. The cured sheets are then separated from the metalplates and also from texture plates, if the latter have been used.Finally, the cured sheets are trimmed to size.

It has been found that sheets made in the manner described above haveunusual properties.

The modulus of rupture is so increased that a sheet of thickness 0.130inch, made with the method and apparatus described, will withstand thesame load before breaking as a sheet 0.155 inch thick, otherwisecomparable but made by the conventional dry shingle process and machine.In other words, for a given breaking strength, it is possible todecrease the thickness of a sheet by about a sixth, with attendant verylarge saving in the cost of materials.

I have found, also, a decreased rate of penetration by water in shinglesmade with the new method and apparatus described. In a standard test todetermine the time required for the penetration of water, under apressure cor- The stack is responding to 20 inches of mercury, the timere- 75 quired for penetration of the water through my improv-ed sheetis'more than 50% longer fthan the time of penetration for a comparablesheet made by the conventional dry shingle process.

Finally, there is a decreased loss of the shaped layer of materialsduring the manufacturing process. This decreased loss is accounted for,in part at least, by the fact that my segments before hydrauliccompression are considerably more coherent than those previously made.

In'the finished asbestos and cement sheet, the asbestos -bres and cementare approximately uniformly mixed. 'I'he asbestos fibres are welldispersed, that is, individualized to a very high degree, so that thereare practically no large clusters of asbestos such as are commonly foundin the dry process asbestos and cement sheets. Also, the asbestos fibresare arranged at random. The fibres in my product give maximum eiectiveness as reenforcing.

Anotherhydraulic cement, as, for example, a calcium aluminate cement(Lumnite), or a mixture of lime and comminuted diatomaceous earth may besubstituted for Portland cement in the compositions described above. Incase the aluminate cement is used, curing is best effected withoutsteaming and without the addition of silica. In case a mixture of limeand diatomaceous earth is used as the cement. no additional silica isrequired and the curing is effected by steaming, as described.

The details given are for the purpose of illustration, not restriction,and variations within the spirit of the invention are intended to beincluded in the scope of the appended claims.

What I claim is:

l. An apparatus for making a brous and cement product which comprises asubstantially air impermeable felting belt, a chamber positioned overthe felting belt, and means for forming a dispersed mixture of fibresand cement in the chamber and for depositing the dispersed mixture as alayer upon the lfelting belt, said dispersing and depositing meansincluding coacting beaters positioned in the chamber over the feltingbelt and arranged in pairs and rotated so as to drive the dispersedmixture in the direction .of said felting belt.

2. An apparatus for making a brous and cement product which comprises asubstantially air impermeable felting belt, an air iilled chamberpositioned over and confining the air over the felting belt, and meansfor forming a dis persed mixture of bres and cement in the air of thechamber and for depositing the dispersed mixture as a layer upon thefelting belt, said dispersing and depositing means including coactingbeaters positioned in the air lled chamber over the felting belt andarranged in pairs and rotated, at points nearest to each other, in thedirection of the felting belt so as to drive the dispersed mixture inthe direction of said felting belt. A

GEORGE B. BROWN.

